1) Field of the Invention
The invention relates to an eight-edged, rotatable and reversible cutting insert having two opposite, substantially square base surfaces which are twisted relative to one another about a central axis running perpendicularly to said base surfaces, and having four identical side surfaces, wherein a main lip is formed between each base surface and each side surface. It also relates to a tool holder for such a cutting insert.
2) Description of the Related Art
A multi-edged cutting body made of a hard cutting material is known from DE-B 1 232 436, said cutting body being formed from two truncated-pyramid-like cutting body halves, the base surfaces of which, located opposite one another while forming four identical side surfaces, are twisted relative to one another. The side surfaces form with both base surfaces a total of eight cutting edges which extend in each case over the entire length of the side surfaces and of the base surfaces. A central hole running at right angles to the base surfaces of the cutting body halves and therefore perpendicularly to the central axis serves to accommodate a screw, by means of which the cutting insert can be fastened in a recess of a tool holder. The four identical side surfaces have flat rake faces which are assigned to and are adjacent to the respective cutting edges and which extend transversely to the central axis along the entire cutting edge and in the direction of the central axis up to the side surface center, in which the two cutting body halves are adjacent to one another.
In the tangential cutting tip used, for example, in a turning tool, the eight cutting edges thereof can be brought into use one after the other by rotating and reversing the cutting tip in the tool holder.
The object of the invention is to specify an eight-edged cutting insert of the type mentioned at the beginning which is improved in particular with regard to a reliable tip seat in a tool holder. Furthermore, a tool holder which is especially suitable for accommodating such a cutting insert is to be specified.